This invention relates to an improved reflector for a lamp such as a fog lamp, wherein the reflector itself distributes light in a desired non-collimated pattern and yet has a continuous surface which is visually smooth.
Prior art vehicular lamps known to the inventors have used either optics in the lens to disperse collimated light laterally from a parabolic reflector, or have used reflectors having obvious joints between various sections of the reflector. See for example Balsillie U.S. Pat. No. 1,639,363, which discloses a reflector in FIG. 1 having a plurality of segments 19-26 which are convexly shaped to disperse light laterally in the region 28.
Melton U.S. Pat. No. 1,814,326 discloses another headlight reflector, which in this case is made up of segments that are discontinuous with respect to adjacent segments. Other patents showing reflectors which are visually segmented to provide desired light distribution are shown in Flaherty U.S. Pat. No. 2,274,405, Morasz U.S. Pat. No. 3,758,770, Sands U.S. Pat. No. 4,494,176, Van Horn U.S. Pat. No. 4,447,865, Dziubaty U.S. Pat. No. 4,293,900 and McReynolds U.S. Pat. No. 4,028,542. In each case, the visually apparent segments on the reflector result in a non-uniform appearance which is objectionable in many applications.
Dorman U.S. Pat. No. 4,149,227 discloses a reflector for a dental surgical lighting system. This reflector is ellipsoidal in shape, and the reflector surface is divided into stripes. Each stripe defines a respective ellipsoid, and the ellipsoids are rotated outwardly with respect to one another as shown in FIG. 6 to spread the reflected light along one axis, thereby enlarging the illuminated area. As shown in FIG. 12, the rotated ellipsoids may have focuses that are offset slightly with respect to one another. Alternately, as shown in FIG. 13, the ellipoidal surfaces may be recalculated to ensure that all of the focuses coincide. Note the discussion at columns 6 and 7, and in particular the discussion at column 6, line 59 through column 7, line 18. The Dorman patent utilizes ellipsoids of revolution rather than paraboloids of revolution, and therefore causes reflected light to converge at the conjugate focus, and to diverge thereafter in both the horizontal and vertical directions. This dispersion pattern is unsuitable for many vehicular lamps. Furthermore, the Dorman patent discloses a reflector which is non-uniform in visual appearance, because of the cusps 51, 50 between adjacent ellipsoids (FIG. 6 ), and therefore does not provide the visually smooth appearance required in many applications.
The present invention is directed to an improved reflector having a visually smooth surface through a portion that occupies at least a quadrant of the reflector, yet which disperses light away from an optical axis in the horizontal direction in a pattern suitable for vehicular lamps.